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Thread: electric assist to hydalulic assist changeover

  1. #1
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    Question electric assist to hydalulic assist changeover

    This must be a repetitive question since the 2003 Z4 introduction. I have a 2005 Z4 3.0 with the 6 speed manual and sport package. Love the car but not the freeway antics of the stock electric assist steering. What does it take to convert the unpopular electric assist steering to a hydraulic assist setup similar to what was introduced in the 2006 M Roadster? For example: Can the M Roadster rack (or, for that matter, a 3 series rack), pump, hoses, reservoir, belts, hardware etc. be successfully adapted to the Z4 with good results? I realize it would not be cheap. Would appreciate your advise.

  2. #2
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    I suggest you find out what is behind the 'freeway antics' you are experiencing, and get it fixed. I have EPS in my car, and love it - no complaints or concerns with it whatsoever. Some prefer the hydraulic setup as they don't feel the EPS provides sufficient feedback. I don't agree, but regardless a different amount of feedback isn't going to have any effect on your cars handling. Take a good look at your tires, pressures, suspension components and alignment. There are known issues of tramlining with the OEM runflat tires (correct tire pressure helps greatly with that), and some owners have had problems with 'sticky steering' in the steering column itself - there is a low cost fix for that by tapping the housing and injecting lubricant.
    Last edited by WestCDA; 04-04-2016 at 02:18 PM.

  3. #3
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    OP, I don't see any reason it can't be done. Expect to swap EVERYTHING from the steering rack through to the steering wheel/column.
    Quote Originally Posted by WestCDA View Post
    Some prefer the hydraulic setup as they don't feel the EPS provides sufficient feedback.
    EPS doesn't "not provide enough feedback" ...it provides no feedback at all

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  4. #4
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    Quote Originally Posted by BimmerBreaker View Post
    ... EPS doesn't "not provide enough feedback" ...it provides no feedback at all
    Simply not true. This isn't a computer controlled 'steer by wire' system, with the steering rack and road wheels independent from a steering wheel controller - it's merely electric assist applied as needed to regular rack and pinion mechanical steering system, which eliminates the need for a power robbing constantly driven hydraulic pump. Like any other manufacturer using EPS (and there are a LOT of them by now), it was tuned by BMW to provide the right amount of assist at the right time, while still providing what they felt was good road feel. The BMW literature of the period will tell you the same.

    http://www.bmwclub.lv/files/06_E85_C...namics.001.pdf

    If you look at the independent E85 reviews of the day you'll find many that specifically compliment the precise feel of the steering system. I agree with them.

  5. #5
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    I'd be curious as well as to what OP's doing or being subjected to on the freeway. As BimmerBreaker mentions, anything can be done...if you have the money. It's not actually a frequent complaint here - it's far more repetitive from people that don't own it.

    I don't have a BMW w/out EPS, so I did a little research on the web:
    http://www.caranddriver.com/features...n-test-feature

    One of the things the article points out is that perhaps other car manufacturers are less concerned with road feel than BMW. My other car (Subaru) doesn't have EPS and I've driven many other older cars that didn't have it as well. I can't compare the EPS to the M's HPS as I've never driven one. Though, I'm not sure what would be happening on a freeway to really make such an impression.

    From the linked BMW pdf above:
    "EPS provides a direct mechanical connection to the steering gear, conveying direct road feel."
    Not so much a signature as a cry for help.

    Hold on, saw this in a cartoon once...think I can pull it off.

  6. #6
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    Maybe this is of help OP? http://forum.roadfly.com/threads/116...blems-unsolved.

    Quote Originally Posted by WestCDA View Post
    If you look at the independent E85 reviews of the day you'll find many that specifically compliment the precise feel of the steering system. I agree with them.
    Mechanical connection or not, it feels extremely numb. Most reports/reviews from the period that I've read (and I've read many) talked very poorly of the steering system, to quote a few:

    "However, its reflexes and communication with the driver are a bit lacking due to a numb electric power steering system" -Edmunds

    "Another problem is the new electric power steering whose feel fades away as speed increases. Sadly, a sports car without steering feel will never be a great sports car, nor a great BMW." -Autozine, 2002

    "The steering, while suitably direct, becomes quite light and flighty at highway speeds, where it also lacks on-centre feel. Employing the Sport mode improves tactility and precision but, overall, the gee-whiz steering electronics fail to deliver." -Drive, 2003

    "Electrically assisted steering was adopted by the Z4 in 2006, and, while we’re not pointing any fingers, we’ve yet to encounter one of these that subjectively equals the old-fashioned hydraulic type." -Motor Trend, 2007

    "True, the runflats rob a little composure and the steering doesn’t have the right level of feel, but it remains a great drive." -Autocar, 2006

    "The steering is quite light until you switch on the Sport setting, at which point it gains more heft to match its accuracy and directness. It still lacks the reassuring weight and feel of a Boxster’s, though." -Automobilemag, 2002


    I could go on... I didn't introduce any bias into my search, I googled "BMW E85 Z4 Review" for the time period 1/1/2002 through 1/1/2009 - to encompass the Z4's production run and possible early press prototypes. Of all the reviews I read, ONE of them could be reported as positive, but they still reported on glaring problems with the system (in that case, it was how the wheel will dance around over rough roads). I love the Z4 overall, but the steering system is - to most - a huge drawback.

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    Quote Originally Posted by BimmerBreaker View Post
    I could go on...
    Well, that might be the case. Admittedly, it seems as the e85 wouldn't be the best choice for track. I've only used it for autocross where the speeds rarely get above 55mph and for the more crucial turns are almost always at a lower speed. Still, the freeway isn't the same as track, though the way some people drive around Seattle maybe it is for OP...

    Without a closed road, I rarely pass 60 on twisty highways in WA for safety reasons. At these speeds my impressions from the road come from many factors including years of driving this z4. Probably I've rarely been in conditions where the short coming of the EPS system are really blatant.

    Still, as for many major modifications concerning the z4 the advice most given is to just buy the M version as once you're into thousands of dollars of modifications for one area you'd realize an overall savings in the end.
    Not so much a signature as a cry for help.

    Hold on, saw this in a cartoon once...think I can pull it off.

  8. #8
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    Meh. I'm with OP. The freeway antics can include sticky steering. If you're going through the expense to replace so many components, why not do it right and get the hydraulic system?

    If you've never driven an M, you don't know what you're missing. That's not intended to insult. The M has the best steering of any car I've ever driven. Take it from a guy with a heavily modified non-M ($20k+ in parts), that clings to his car despite no logical reason to keep it (too many cars, already have the M, blah blah blah). If there was one thing I could change about the non-M, it would be the steering. And frankly, it's why I haven't bought a new BMW. The only new performance cars that interest me are well out of my price range, and I can't justify paying more money for less of an experience. Electric steering is terrible.

    If there's a way to get hydraulic steering on a non-M, I would love to hear about it. The ECU expects electric steering, so I imagine there's more to it than just fitting the hardware.
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  9. #9
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    I don't believe I have a sticky steering column. Using recommended (33f/36r) tire pressures on new set of Yokohama Advan Sports. Problems increase when tire/road temps increase. It's like the EPS cannot keep up with sticky tires.

  10. #10
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    Quote Originally Posted by pokeybritches View Post
    The ECU expects electric steering, so I imagine there's more to it than just fitting the hardware.
    Curious what you mean by that. As in the ECU will send signals to what it thinks is an electric steering assist motor?

    As I see it, if the full hydraulic setup was installed from the M it will work... and it will have the steering angle sensor and everything, so it shouldn't do anything too weird. But now I'm thinking it'll throw an EPS light. Maybe it can be coded out?

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    Quote Originally Posted by Jarold Bowerman View Post
    I don't believe I have a sticky steering column. Using recommended (33f/36r) tire pressures on new set of Yokohama Advan Sports. Problems increase when tire/road temps increase. It's like the EPS cannot keep up with sticky tires.
    I've driven in 100 degree heat with Dunlop Direzza's (200 treadwear) and not noticed any problems with steering. I've also done autocross with treadwear 60 tires and not noticed anything wrong. Maybe it's something specifically wrong with your car and not the technology exactly.
    Not so much a signature as a cry for help.

    Hold on, saw this in a cartoon once...think I can pull it off.

  12. #12
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    An intermittent problem is a dreaded term in auto mechanics. This last Sunday I took the Z4 out for an early morning freeway test run under cool conditions. I was expecting the erractic steering play of previous days but was pleasantly surprised to feel a solid and responsive system. I was causiously optimistic. I waited later in the day until temperatures were warmer and made another run with the same positive results. I could have driven this wonderful machine all day but for the increasing Seattle traffic. I never made any adjustments. Not complaining but can I expect this electric assist steering system to continue the flawless performance or might it jump back into an erractic state? Thanks.

  13. #13
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    I see no reason to expect it to continue operating without problem if there was something wrong with the system in the past. In my experience, gremlins like this may disappear for a short while but they will come back. It most likely can be fixed with the grease injection method based on what you are saying though.

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  14. #14
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    Quote Originally Posted by BimmerBreaker View Post
    Curious what you mean by that. As in the ECU will send signals to what it thinks is an electric steering assist motor?

    As I see it, if the full hydraulic setup was installed from the M it will work... and it will have the steering angle sensor and everything, so it shouldn't do anything too weird. But now I'm thinking it'll throw an EPS light. Maybe it can be coded out?
    The EPS light is what I was referring to. I haven't compared parts on realoem yet, but steering angle sensor was one.

    I may go forward with the swap next year and address the warnings as they surface.
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    Quote Originally Posted by pokeybritches View Post
    I may go forward with the swap next year and address the warnings as they surface.
    If you do this please document it thoroughly and share.

    I'm in the same boat with you - I really love my 3.0si, but the electric steering bothers me. It's not that it's electric per se. It's not the lack of feel, although that is certainly the case; there just ain't much coming back to the hands from the front of the car. But I drive as much through my butt as I do my hands, and the zed has great, errr, 'butt feel', so I'm happy enough when it comes to being connected with the car's dynamics. It's the nervousness and constant need to make minor corrections that really bug me. I think I'm going to give the front suspension a thorough going over just to see if there something amiss, like FCABs. The mileage on my car is low, but it's nigh on 10 years old so who knows.

  16. #16
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    ^^^ that was my problem with the Z4 steering too. It was pretty direct, it responded well and pointed the car where I wanted it to point. The connection from me to the wheels was great. But it was the lack of feedback from the wheels back to me is what bothered me. That is something that simply can't be replicated with an electric steering system.

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  17. #17
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    This diagram may help.
    Attached Images Attached Images
    VF Engineering Z4 3.0i | ESS VT2-500 Z4M | G-Power SK I Z4M | 996tt

  18. #18
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    Yes, it can be done (I did it) and it's a significantly better system.

    You will need the Z4M (roadster or coupe) rack, the intermediate shaft (cannot reuse the non-M shaft as the rack end is a different size), all hoses, and a PS pump. Everything is bolt on.

    You must leave ALL electronics in place otherwise you will get an error code (unless you can get someone to tune it out). You will need to take the steering column apart and remove the drive gear off the motor (to prevent the motor from applying assist to the column) and then reassemble so the system "works" but doesn't apply assist.

    It's not hard, it's about $1000-$1500 in parts, and takes about half a day to do the conversion.
    Chris

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    Quote Originally Posted by V8Z4 View Post
    Yes, it can be done (I did it) and it's a significantly better system.

    You will need the Z4M (roadster or coupe) rack, the intermediate shaft (cannot reuse the non-M shaft as the rack end is a different size), all hoses, and a PS pump. Everything is bolt on.

    You must leave ALL electronics in place otherwise you will get an error code (unless you can get someone to tune it out). You will need to take the steering column apart and remove the drive gear off the motor (to prevent the motor from applying assist to the column) and then reassemble so the system "works" but doesn't apply assist.

    It's not hard, it's about $1000-$1500 in parts, and takes about half a day to do the conversion.
    Wow, that is an awesome bit of news. How did you handle driving the pump? When you say "bolt on" is it really that clean of an installation process or are there little items such as brackets and whatnot that need to be sourced or fashioned? Is the $1500 pricetag for new parts?

  20. #20
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    100% bolt on. The non-M z4s have an idler (bracket and pulley) in place of the PS pump. Simply unbolt the idler (bracket and pulley), mount the pump (with it's associated bracket), and put on the correct belt (I don't remember if I reused the old belt or got a new belt...).

    $1500 is a mix of new and used parts (this is a rough number...it's been a while since I did the swap). A remanufactured Z4 roadster rack is ~$500, new pump is around $250, reservoir is $100, hoses are another $100-$150, intermediate shaft is $150-$350 (depending on where you get it/what you buy... I built my own using aftermarket universal joints and splined shaft).

    The pump and hoses don't have to be Z4M specific. I used a pump and hoses from an E46 325i. Make sure you get the same year/series pump and hoses. There was a switch somewhere along the way.
    Chris

  21. #21
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    Quote Originally Posted by V8Z4 View Post
    Yes, it can be done (I did it) and it's a significantly better system.

    You will need the Z4M (roadster or coupe) rack, the intermediate shaft (cannot reuse the non-M shaft as the rack end is a different size), all hoses, and a PS pump. Everything is bolt on.

    You must leave ALL electronics in place otherwise you will get an error code (unless you can get someone to tune it out). You will need to take the steering column apart and remove the drive gear off the motor (to prevent the motor from applying assist to the column) and then reassemble so the system "works" but doesn't apply assist.

    It's not hard, it's about $1000-$1500 in parts, and takes about half a day to do the conversion.
    I

  22. #22
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    I know this is an old thread but this is just what I have been looking for. I knew I could do the actual conversion from reading the z4 forum and Raymond Harpers posts but I didn't know what to do with the electric motor and the electronic side of things to prevent warning lights, I thought there would be a lot of expensive recoding to do, I cant believe the solution is so simple.
    How easy is it to drop the steering column and remove the drive gear of the motor?


  23. #23
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    Quote Originally Posted by garybb1 View Post
    I know this is an old thread but this is just what I have been looking for. I knew I could do the actual conversion from reading the z4 forum and Raymond Harpers posts but I didn't know what to do with the electric motor and the electronic side of things to prevent warning lights, I thought there would be a lot of expensive recoding to do, I cant believe the solution is so simple.
    How easy is it to drop the steering column and remove the drive gear of the motor?

    I'm not sure what all is involved with the coding, so I wouldn't go so far as to say coding isn't needed. I would assume that if you simply removed the drive pinion off the motor and left it in place, there wouldn't be any coding necessary (computer would still think the electric steering was working as normal). But, I can't confirm.

    Personally, I found it's overall quite easy to get the steering column out. The hardest part is there is one bolt without a head that is quite tight, so it's quite difficult to remove that one bolt. Once the bolt is out, everything just slides right out (provided you unbolt the other bolts). SO, IF that one bolt comes off easily then the whole project could be done in an evening (hour or two). If that bolt is a pain, well...
    Chris

  24. #24
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    I originally thought it might b like a closed loop system where the electronics would expect feedback from the steering column.
    Can anyone else confirm the motor can be left in place?
    I guess if you carried out the conversion leaving the motor in place and it never through up any fault lights etc it must work[
    QUOTE=V8Z4;29643612]I'm not sure what all is involved with the coding, so I wouldn't go so far as to say coding isn't needed. I would assume that if you simply removed the drive pinion off the motor and left it in place, there wouldn't be any coding necessary (computer would still think the electric steering was working as normal). But, I can't confirm.

    Personally, I found it's overall quite easy to get the steering column out. The hardest part is there is one bolt without a head that is quite tight, so it's quite difficult to remove that one bolt. Once the bolt is out, everything just slides right out (provided you unbolt the other bolts). SO, IF that one bolt comes off easily then the whole project could be done in an evening (hour or two). If that bolt is a pain, well...[/QUOTE]

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